U.S. Pat. Nos. 6,302,485, 7,322,646, 7,669,932, and 7,758,126 disclose a headrest which is folded when a single button is pushed. U.S. Pat. Nos. 6,302,485, 7,322,646, 7,669,932, and 7,758,126 have a problem in that the vertical height of the headrest cannot be adjusted using a button that folds the headrest.
U.S. Pat. Nos. 6,880,890 and 6,910,740 disclose a headrest which, when a button is pushed, is rotated so that an inclination of the headrest is adjusted. U.S. Pat. Nos. 6,880,890 and 6,910,740 have a problem in that the vertical height of the headrest cannot be adjusted using a button that adjusts a forward/backward angle.
U.S. Pat. Nos. 6,068,337, 7,306,287, 7,621,598, and 5,711,579 and U.S. Laid-Open Patent No. 2011-0148171 disclose a headrest of which a vertical height is adjusted when a button is pushed. U.S. Pat. Nos. 6,068,337, 7,306,287, 7,621,598, and 5,711,579 and U.S. Laid-Open Patent No. 2011-0148171 have a problem in that a position of the headrest in a forward/backward direction cannot be adjusted through a vertical height adjusting button.
U.S. Pat. No. 4,265,482 discloses a headrest of which a forward/backward position is adjusted when a button is pushed. U.S. Pat. No. 4,265,482 has a problem in that the vertical height of the headrest cannot be adjusted through a forward/backward position adjusting button.
U.S. Patent Laid-Open Publication No. 2012-80926 discloses a configuration capable of moving a headrest upward/downward and forward/backward using a single button. U.S. Patent Laid-Open Publication No. 2012-80926 makes the headrest movable forward/backward by deforming a leaf spring interlocked with the lock plate to release locking. The U.S. Laid-Open Patent Publication No. 2012-80926 has a problem in that since the internal structure of the headrest is complicated, the assemblability is poor and the price of a product is increased.
U.S. Pat. No. 7,267,407 discloses a structure which includes a bottom cover having a shape corresponding to a bottom opening, and a ratchet assembly disposed between the bottom cover and the headrest such that the height of the headrest is adjusted by moving a ratchet post in a locking direction or a locking releasing direction. The ratchet assembly includes a bottom portion that operates the latchet assembly, the bottom cover includes a bezel unit that surrounds the bottom portion and disposed outside the headrest, the bottom portion is positioned below an outer surface of the headrest, and the height adjusting device is disposed outside the headrest.
In a headrest of Korean Patent Application No. 2011-0089135 (not published), a middle cover that is formed with a hollow portion, a lock pin that passes through the hollow portion, a rear plate that penetrates the hollow portion, and a lock plate that is positioned to be movable leftward/rightward are disposed within a cover of the headrest and the headrest is provided with a button that presses the lock plate. In Korean Patent Application No. 2011-0089135, an adjusting device that adjusts a height and a forward/backward position of the headrest is disposed inside the headrest, and the middle cover is not formed with a bezel unit that encloses the lock plate and is disposed outside the middle cover, by which Korean Patent Application No. 2011-0089135 is differentiated from U.S. Pat. No. 7,267,407.
However, the headrest of Korean Patent Application No. 2011-0089135 has problems in that the front cover is installed to be movable forward/backward in relation to the rear cover to generate a gap in the device, and a link structure is used thereby making the structure complicated, deteriorating the assemblability, and increasing the price of a product. In addition, in Korean Patent Application No. 2011-0089135, since teeth are formed integrally with the front cover, the front cover and the teeth should be formed of the same material. As a result, the weight of the device is increased and a fastening force is poor.